Back in August of 2014, a team of MIT Researchers released a video which some dubbed the, “Mary Had A Little Lamb” video. It described an experiment by MIT researchers to extract audio from only the vibrations of a plant, potato-chip bag, laptop earbuds, and other objects.
The significance of the nursery rhyme name was to acknowledge one of the first phrases spoken in 1878 by Thomas Edison into his first phonograph. But the rhyme also acknowledges (perhaps unknowingly) the differences between visual microphones, which we’ll cover here, and optical microphones – to be covered in a future story. Both technologies have a modern connection to Edison.
The “Mary had a Little Lamb” video used a then experimental technology known as a visual microphone. It worked by collecting and converting vibrational data back into audio signals. The microphone picked up input sound caused by air pressure fluctuations at the surface of an object. High speed cameras were used to capture the fluctuating movement on film at a rate of between 1kHz-20kHz. The resulting recorded video was then processed by a proprietary algorithm to recover the original sound.
|Image Source: The Public Domain Review|